Trial of dextromethorphan/quinidine to treat levodopa-induced dyskinesia in Parkinson's disease

Mov Disord. 2017 Jun;32(6):893-903. doi: 10.1002/mds.26976. Epub 2017 Mar 30.


Background: Nondopaminergic pathways represent potential targets to treat levodopa-induced dyskinesia in Parkinson's disease (PD). This pilot-study (NCT01767129) examined the safety/efficacy of the sigma-1 receptor-agonist and glutamatergic/monoaminergic modulator, dextromethorphan plus quinidine (to inhibit rapid dextromethorphan metabolism), for treating levodopa-induced dyskinesia.

Methods: PD patients were randomized to dextromethorphan/quinidine (45 mg/10 mg twice daily)/placebo in two 2-week double-blind, crossover treatment periods, with intervening 2-week washout. After 14 days, a 2-hour intravenous levodopa-infusion was administered. Patient examinations were videotaped before infusion ("off" state) and every 30 minutes during and afterwards until patients returned to "off." The primary endpoint was dyskinesia-severity during infusion measured by Unified Dyskinesia Rating Scale part 3 area-under-curve scores (blinded expert rated). Additional endpoints included other dyskinesia/motor assessments, global measures of clinical-change, and adverse-events.

Results: A total of 13 patients were randomized and completed the study (efficacy-evaluable population). Dyskinesia-severity was nonsignificantly lower with dextromethorphan/quinidine than placebo during infusion (area-under-curve 966.5 vs 1048.8; P = .191 [efficacy-evaluable patients]), and significantly lower in a post-hoc sensitivity analysis of the per-protocol-population (efficacy-evaluable patients with ≥ 80% study-drug-compliance, n = 12) when measured from infusion start to 4-hours post-infusion completion (area-under-curve 1585.0 vs 1911.3; P = .024). Mean peak dyskinesia decreased significantly from infusion-start to return to "off" (13.3 vs 14.9; P = .018 [efficacy-evaluable patients]). A total of 9 patients rated dyskinesia "much/very much improved" on dextromethorphan/quinidine versus 1-patient on placebo. Dextromethorphan/quinidine did not worsen PD-motor scores, was generally well tolerated, and was associated with more frequent adverse events.

Conclusion: This study provides preliminary evidence of clinical benefit with dextromethorphan/quinidine for treating levodopa-induced dyskinesia in PD. Larger studies with a longer treatment duration need to corroborate these early findings. © 2017 International Parkinson and Movement Disorder Society.

Keywords: AVP-923; Parkinson's disease; Unified Dyskinesia Rating Scale; dextromethorphan/quinidine; levodopa-induced dyskinesia.

Publication types

  • Randomized Controlled Trial

MeSH terms

  • Aged
  • Antiparkinson Agents / adverse effects*
  • Cross-Over Studies
  • Dextromethorphan / administration & dosage
  • Dextromethorphan / adverse effects
  • Dextromethorphan / pharmacology*
  • Double-Blind Method
  • Drug Therapy, Combination
  • Dyskinesia, Drug-Induced / drug therapy*
  • Dyskinesia, Drug-Induced / etiology
  • Enzyme Inhibitors / administration & dosage
  • Enzyme Inhibitors / pharmacology*
  • Excitatory Amino Acid Antagonists / administration & dosage
  • Excitatory Amino Acid Antagonists / adverse effects
  • Excitatory Amino Acid Antagonists / pharmacology*
  • Female
  • Humans
  • Levodopa / adverse effects*
  • Male
  • Middle Aged
  • Outcome Assessment, Health Care*
  • Parkinson Disease / drug therapy*
  • Pilot Projects
  • Quinidine / administration & dosage
  • Quinidine / adverse effects
  • Quinidine / pharmacology*


  • Antiparkinson Agents
  • Enzyme Inhibitors
  • Excitatory Amino Acid Antagonists
  • Levodopa
  • Dextromethorphan
  • Quinidine

Associated data